The regulation of photosynthetic membrane (chromatophore) formation in Rhodopseudomonas capsulata will be studied by the methods of biochemical genetics. Carotenoids are an integral component of chromatophores, and the molecular details of their synthesis and regulation will be investigated by assaying carotenoid biosynthetic enzymes under various conditions which affect membrane composition and in various mutants with altered regulatory responses. The coordination between carotenoid and bacteriochlorophyll biosynthesis will be probed by biochemical and genetics analyses of mutants with pleiotropic changes in both systems and kinetic analyses of regulatory events. Genetic studies of the photopigment region of the chromosome shall be carried out using the R. capsulata gene transfer system. The genetic system itself will be studied in an attempt to determine whether the genes involved are clustered or dispersed on the bacterial chromosome. Genes coding for elements of the photosynthetic apparatus will be isolated from R-primed plasmids and cloned. Cloned fragments will serve as probes for studies of gene location and transcription.